Cryo-EM structure of the polycystic kidney disease-like channel PKD2L1

Abstract

PKD2L1, also termed TRPP3 from the TRPP subfamily (polycystic TRP channels), is involved in the sour sensation and other pH-dependent processes. PKD2L1 is believed to be a nonselective cation channel that can be regulated by voltage, protons, and calcium. Despite its considerable importance, the molecular mechanisms underlying PKD2L1 regulations are largely unknown. Here, we determine the PKD2L1 atomic structure at 3.38 Å resolution by cryo-electron microscopy, whereby side chains of nearly all residues are assigned. Unlike its ortholog PKD2, the pore helix (PH) and transmembrane segment 6 (S6) of PKD2L1, which are involved in upper and lower-gate opening, adopt an open conformation. Structural comparisons of PKD2L1 with a PKD2-based homologous model indicate that the pore domain dilation is coupled to conformational changes of voltage-sensing domains (VSDs) via a series of π–π interactions, suggesting a potential PKD2L1 gating mechanism.

The ion channel function of polycystin‐1 in the polycystin‐1/polycystin‐2 complex

“…In the case of PC1, the detached CTF may also have NTF-independent channel function when assembled with PC2 (Fig 4). The cryo-EM structure of PC1/PC2 was solved using a truncated PC1 fragment containing the CTF lacking the intracellular C-terminal tail [44]. The structure shows that this PC1 fragment assembles with PC2 into a channel-like complex [44], consistent with our functional data.…”

“…The cryo-EM structure of PC1/PC2 was solved using a truncated PC1 fragment containing the CTF lacking the intracellular C-terminal tail [44]. The structure shows that this PC1 fragment assembles with PC2 into a channel-like complex [44], consistent with our functional data. We further show that the shorter fragment, TLD, retains channel function when associated with PC2 ( Fig 4F-H).…”

“…In combination, the results from this study with our previous finding of the 1:3 subunit stoichiometry [40], and the recently published cryo-EM structure [44], have significantly advanced the understanding of channel function of PC1/PC2. The GOF channel generated here provides a platform for the study of the function and regulation of this complex.…”

“…This is mainly due to the lack of knowledge on the channel activation mechanism, making functional analysis very challenging. Interestingly, the structure of PC2_F604P is very similar to an open structure of TRPP3 [44], suggesting that the F604P mutation results in a conformational change reflecting the natural gating of PC2. PC2_F640P gave rise to robust whole-oocyte currents when expressed in Xenopus laevis oocytes [11,22,43].…”

“…The cryo-EM structure showed that the F604P mutation leads to twisting and rotation of the distal S6 helix and opening of the lower pore gate [43]. Interestingly, the structure of PC2_F604P is very similar to an open structure of TRPP3 [44], suggesting that the F604P mutation results in a conformational change reflecting the natural gating of PC2. In the current study, taking advantage of another GOF PC2 mutant, we were able to reliably record channel activity of PC1/PC2, study its ion permeability, and, for the first time, dissect the function of PC1 in this channel.…”